1. Field of the Invention
This invention relates to an inkjet printing device and a method for replacing a print head of an inkjet printing device. More particularly, this invention relates to techniques for connecting an ink tank and a print head with a supply path such as an ink supply tube and preventing ink from leaking from the supply path when the print head is removed from the supply path for print-head replacement or the like.
2. Description of the Related Art
In the inkjet printing devices, there is known a method for connecting an ink tank and a print head with an ink supply path such as a tube to supply ink from the ink tank to the print head. In this method, the ink tank is typically mounted in a fixed position within the inkjet printing device. The ink tank and the print head mounted on a carriage are connected to each other by use of the ink supply path such as the tube, thereby supplying the ink from the ink tank to the print head. In the following, this method is referred to as an “off-carriage tank method” for the sake of convenience.
The off-carriage tank method has advantages of eliminating the need for ensuring a large area for placement of a main ink tank on the carriage, not imposing a large load at the carriage movement, and storing a large amount of ink to be supplied to the print head.
However, this method has a risk of residual ink in the print head or the ink supply path leaking from there to result in an ink stain damaging an area around the print head or the ink supply path when or after the print head is or has been removed. Of methods implemented to address such disadvantages, for example, a method uses an on-off valve placed in a pressurization path for an ink supply to release the pressure in the ink supply path when the print head is replaced. Another method uses means for varying the inner capacity of the ink supply path to adjust the pressure in the ink supply path. Specifically, in any of these methods, the pressure in the ink supply path when the print head is removed is reduced to be lower than that at the ink supply, thus preventing the ink leakage from the ink supply path or the like.
However, in any of the methods, the pressure in the ink supply path can be reduced only to an atmospheric pressure at a maximum. Accordingly, when the print head is removed under such conditions, risks of scattering and dripping of the residual ink remaining in the joint between the print head and the ink supply path still remain. The methods provide an inadequate reduction in an ink stain damaging the surroundings.
To address this, Japanese Patent Laid-Open No. 2001-018412 discloses a structure including an ink-suction hole provided in an ink supply needle and sucking means provided in an ink supply path. Specifically, Japanese Patent Laid-Open No. 2001-018412 discloses the structure in which, upon removal of the print head, a negative pressure is generated in the ink supply path and thereby the generated negative pressure acts in the print head through the ink supply hole formed in the ink supply needle, thus returning the ink in the print head back into the ink supply path.
However, employment of such a structure including the ink-suction hole provided in the ink supply needle and the negative-pressure generating mechanism for suction provided in the ink supply path, as described in Japanese Patent Laid-Open No. 2001-018412, provides a complicated structure of an ink supply unit because of replacement of the print head. As a result, this structure brings in complexity, an increase in size or cost, and the like in the inkjet printing device.